A colony of pig-tailed macaques (Macaca nemestrina) has been established by the Regional Primate Research Center at the University of Washington for research on aging. The colony's purpose is to allow a longitudinal, multidisciplinary study of the biology of aging in the pig-tailed macaque as a nonhuman primate model of human aging processes. It consists of 72 animals in four age groups representing young, middle-aged, and old adults. Periodic access to the animals, blood samples, and innocuous biopsy specimens will be provided to collaborating investigators for studies on basic mechanisms relating to immunosenescence, atherosclerosis, diabetes, obesity, osteoporosis, cognitive behavior, social behavior, neural aging, the genetic control of longevity, and other areas of interest. Beginning in early 1981, half of the animals in the colony will be maintained on a typical American diet and half continued on a typical monkey chow diet for five years to allow investigators to evaluate the interacting influence of aging and nutrition on variables that interest them. The cost-effectiveness of the colony as a research resource will be maximized by use of the same animals for multiple, scientifically compatible studies and by establishing a central computerized data base to allow investigators studying related aspects of aging and disease to integrate their findings.